Development of structure/property relation based on surface thermodynamic properties of alkyl-pyridine and aliphatic amines

Abstract

In this article, available experimental surface entropy, surface energy, and surface tension values were used to study the structure/property relation in pyridine, its alkyl derivatives, and linear aliphatic amines. Dipole moment was employed as molecular descriptor. Density functional theory and polarizable continuum model were used to calculate dipole moments in gas and in liquid states, respectively. Surface entropies importantly conform to dipole moments and to the trend characteristics of molecular structures. The decrease of surface entropy with alkyl chain length indicates more aggregation and alignment of surface molecules; similarly the decrease in surface tension suggests the non-polar part exposing more to the vapor side of the interface. Applying these to amines substantiates structure/property relation based on surface properties and dipole moment. Møller–Plesset theory and density functional theory were used to calculate the dipole moment and both correlate adequately with surface properties. These results suggest treatment of surface energy and surface entropy as part of usual qualitative prediction of solvation capability of liquids.